Recently, McKeown et al. reported the synthesis of a new type of polymer, termed polymers of intrinsic microporosity (PIMs), with a randomly contorted molecular structure, bridging the void between microporous and polymeric materials. The rotational freedom of these PIM materials has been removed from the polymer backbone. These polymers exhibit properties analogous to those of conventional microporous materials including large and accessible surface areas, interconnected micropores of less than 2 nm in size, as well as high chemical and thermal stability, but, in addition, possess some favorable properties of conventional polymers including good solubility and easy processability for the preparation of polymeric membranes. Polymeric membranes have been prepared directly from some of these PIMs and both the liquid and gas separation performances have been evaluated. Membranes from PIMs have shown exceptional properties (e.g. extremely high gas permeability) for separation of commercially important gas pairs, including O2/N2 and CO2/CH4. The exceptionally high permeability of gases arises from the rigid but contorted molecular structures of PIMs, frustrating packing and creating free volume, coupled with chemical functionality giving strong intermolecular interactions. Two published PCT patent applications provide further detail: WO 2005/012397 A2 and WO 2005/113121 A1, both applications incorporated by reference in their entireties. Membranes from PIMs, however, have much lower selectivities for commercially important gas pairs, such as O2/N2 and CO2/CH4, although their gas permeabilities are significantly higher than those of commercial polymeric membranes from glassy polymers such as CA, polyimides, and polyetherimides.
Most recently, Guiver et al. reported CO2-philic tetrazole group functionalized polymer nanosieve membranes (TZPIMs) for CO2-capture applications. The TZPIM membrane materials were prepared by [2+3] cyclo-addition modification of PIM-1 polymer containing an aromatic nitrile group with an azide compound. The TZPIM membranes showed enhanced CO2-philic separation selectivities due to interactions between CO2 and the tetrazole compared to PIM-1 membrane. See NATURE MATER., 2011, 10, 372.
The following reactions illustrate the preparation and structures of PIM-1 polymer and the TZPIM polymer, respectively.

The present invention involves a UV-cross-linking method to further improve the performance of the membrane with improvements to selectivity, chemical resistance, and long-term performance stability of TZPIM membranes. In particular, particularly the selectivities for separation of gas pairs such as CO2/N2, CO2/H2, CH4/N2, H2/CH4, H2S/CH4, O2/N2, and CO2/CH4 are improved through the formation of interpolymer-chain-connected cross-linked networks.